In search of an energy yardstick

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Earlier this fall, Google made an announcement that in many ways foretells the future of data center efficiency metrics. The search giant not only disclosed its total power consumption and carbon emissions (mostly attributable to its data centers), but also released estimates of its per-user and per-search energy consumption. With this information -- and given that a billion Google searches occur per day -- it was possible to calculate that searches account for 12.5 million watts of the company's 260 million watt total.

The idea of quantifying the kilowatts of energy required to perform a useful unit of work is now considered the holy grail of data center metrics. The most widely used metric today -- The Green Grid's Power Usage Effectiveness (PUE) measure -- compares the amount of data center energy consumed by IT equipment to the facility's total usage; but no metric yet reveals energy consumed per unit of work, mostly because it is difficult to define a standard "unit of work."

"For cars, it's miles per gallon, but for hardware, is it a MIP or bits transmitted per second? The industry hasn't zeroed in on what 'work' is," says Steve Press, executive director of data center facilities at Kaiser Permanente . "PUE doesn't tell you what work the data center is doing -- it could be blocking virus traffic or moving data for the National Weather [Service]. Once we settle on [that], it will have a big effect on overall competitiveness."